For many years, visual display devices have been known that permit the sequential display of a plurality of coded images by a sequential completion or uncoding of those coded images by a shutter member. These devices can be grouped into two main categories. The first category comprises moveable display devices wherein an image member is slidably retained adjacent to a shutter member to bring about the sequential completion of images while visual display devices that exploit the principles of parallax displacement display a series of images without relative movement form the second category.
In either type of device, a plurality of interposed coded images are disposed on an image member while a shutter member has a plurality of ideally opaque shutter elements disposed thereon. The shutter elements are separated by a plurality of translucent, ideally transparent, viewing elements. Taken alone, the interposed coded images may have the appearance of incoherent narrow strips or, possibly, dots. Further background can be gained by a review of the present inventor's U.S. Pat. No. 5,901,484, which is expressly incorporated herein by reference.
In intended operation, the shutter elements perform dual, equally critical functions. By their opaque nature, the shutter elements are intended to block from view all but one of the interposed coded images, which may be termed an active image. Just as importantly, however, the plurality of shutter elements bridge the gaps between the coded strips that comprise the active image to complete and thereby uncode the active image.
When the image member and the shutter member are moved relative to each other a predetermined amount, either through relative movement or parallax displacement, the strips of the previously active image are concealed whereby the next succeeding coded image assumes the fleeting position as an active image. This phenomenon will continue through a cycle comprising the number of coded images that are disposed on the image member whereupon the first coded image will again appear thereby signaling the start of a new, identical cycle.
In moveable display devices, the sequential image change is accomplished by a sliding of the shutter member relative to the image member, either manually or by machine. In these devices, the observer and the display device need not move relative to one another. The mere sliding of the shutter member relative to the image member is all that is required for displaying a series of images to the observer.
In a markedly different, arguably opposite, manner, visual display devices that are operable without relative movement typically fix the image member relative to the shutter member and display an image change to an observer by creating only the perception of relative movement between the image member and the shutter member, which may be termed a parallax displacement. This parallax displacement can be realized by changing the position of the shutter member relative to the image member from the viewpoint of the observer. Accordingly, devices employing parallax displacement commonly space the shutter member a given distance over the image member and then give the appearance of image change when an observer travels past the device (i.e., the observer walks by the device), when the device travels past an observer (i.e., the device is mounted on a moving vehicle), or when the device is turned about an axis generally parallel to the shared lengthwise orientation of the shutter elements and the coded images. Hereinafter, this axis shall be termed the polar axis of the visual display device.
The astute observer will realize that a given device's ability to display coherent images is inherently dependent on the device's ability to maintain precise registration between the shutter member and the image member. Furthermore, this need for precise registration becomes particularly acute where an increased plurality of images are sought to be displayed because doing so typically demands that the strips comprising the coded images be narrowed to accommodate an increased number of adjacent strips or images.
Accordingly, for many decades, achieving and maintaining precise registration between shutter elements and coded images in image display devices has been a recognized need and an explicit goal of a multiplicity of inventors. Notably, until the invention disclosed and protected by U.S. Pat. No. 5,901,484 to the present inventor, doing so proved to be a challenge that was difficult to meet. Proposed solutions by prior art inventors proved to be undesirably complex, cumbersome, and, in some cases, of dubious effectiveness. However, because movement of the shutter member relative to the image member need not be addressed, achieving and maintaining alignment or registration in visual display devices employing parallax displacement has proven to be a more realizable goal.
Nonetheless, even with alignment achievable and even with a large plurality of such devices disclosed by the prior art, visual display devices employing parallax displacement have suffered and to date continue to suffer from a number of limitations and disadvantages. One principal disadvantage is that such visual display devices are capable of presenting only finite animated sequences to the observer. In prior art displays, the image member is imprinted on semi-translucent material that is designed to catch and maximize the back light to provide a clear image. When so illuminated, these devices may be considered to be partially silhouetted. Stated more particularly, the shutter layer is silhouetted against the illuminated image layer. Unfortunately, because the image member in these traditional displays is semi translucent, not clear, an acceptably crisp image can be perceived only when the image member is behind the shutter layer, never in front. Furthermore, in prior art devices it is a common practice to make the more distant of the shutter elements or the coded images slightly wider in pitch so that the image converges at a given viewing distance. Such displays can not be viewed clearly from the non-converging side regardless of whether the material is translucent or semitranslucent. With this, the image member and the shutter member can not be interchanged, and these prior art devices may well be considered one-sided displays.
Disadvantageously, the one-sided displays of the prior art are limited to a finite image sequence that is displayed with each given amount of parallax displacement. Once the limit of parallax displacement is realized in a one-sided device (i.e., the observer has walked to the end of the display or the display has been rocked through a given angle), further parallax displacement can be achieved only by reversing the previously traveled course and reversing the previously experienced image sequence. Continuous animation is precluded.
Notably, the desirability of achieving continuous animation in a visual display device has been long felt. Accordingly, a number of inventors have attempted to provide just such a display device. For example, the prior art long ago disclosed the zoetrope, which comprises a rotating slotted drum, and the phenakistascope, which comprises a rotating slotted disk. Still further, the prior art reveals a device called a praxinoscope that comprises a rotating drum with a multi-faceted mirrored hub. Advantageously, when rotated, each of these devices present an observer with a continuously animating sequence of images. Disadvantageously, however, these prior art devices are relatively complex in construction and, therefore, limited in use and applicability, expensive to manufacture and sell, and prone to damage and malfunction.
Based on the foregoing, one will appreciate that a visual display device capable of employing parallax displacement to provide a continuous, non-reversing animated sequence would represent a significant advance over the prior art by combining the relative simplicity of a parallax displacement- type visual display device with the enhanced display characteristics typical of more complex prior art devices. Indeed, such a device could reasonably be considered a new, albeit exceedingly and advantageously simple, motion picture machine.